Transport Flashcards
2.51: What is diffusion?
Passive net movement of particles down the concentration gradient (from region of high concentration to region of low concentration) until equilibrium
2.51: Why can simple, unicellular organisms rely on diffusion for movement of substances in and out of the cell?
- As Unicellular organisms are composed of a single cell, they have a larger surface area in relation to their volume, and hence have a large surface area to volume ratio
- With a large surface area to volume ratio, Unicellular organisms therefore have efficient rate of diffusion, allowing cell to rely solely on diffusion to transport necessary substances in and out of the cell
2.51: What are the common features of exchange surfaces?
- Thin Cell Walls
Thin cell walls (one cell thick) to minimise distance of diffusion, increasing the rate of diffusion - Large Surface Area to Volume Ratio
Unicellular organisms are commonly long, thin, flat or folded to increase surface area to volume ratio, increasing the rate of diffusion - Moist
Unicellular organisms have moist membranes to allow substances to diffuse easily
2.52: Why do we not need a transport system for single-cellular organisms?
- In single-celled organisms, diffusion is fast enough to transport substances over short distances across cells.
- As organisms get bigger, diffusion becomes too slow to transport substances over longer distances fast enough to meet the survival needs of the organisms
- Transport system - for faster long-distance transport.
2.52: Why do we need a transport system for multicellular organisms?
- As Multicellular organisms are composed of more than one cell, they have a small surface area in relation to their volume, and hence have a small surface area to volume ratio
With a small surface area to volume ratio, - – Multicellular organisms therefore have inefficient rate of diffusion, preventing cell to rely on diffusion to transport necessary substances in and out of the cell (rate of metabolism will exceed rate of exchange of vital materials and wastes) - Hence, Multicellular organisms rely on transport systems to provide a constant supply of necessary substances through a medium to their cells via an exchange surface
2.59: What is the composition of the blood?
- Red blood cells
- White blood cells
- Plasma
- Platelets
2.59: What is the function/structure of red blood cells?
Transports Oxygen in Haemoglobin of cell from Lungs to respiring cells for aerobic respiration
2.59: What is the function/structure of white blood cells?
Composed of two types of cells - Phagocytes that engulf and digest pathogens, and Lymphocytes that produce antibodies to deactivate antigens of Bacteria
2.59: What is the function/structure of the platelets?
Cell fragments involved in blood clotting
2.59: What is the function/structure of the plasma?
Medium of transport that carries Carbon Dioxide, digested food, Urea, Hormones and Heat
2.60: How does plasma transport carbon dioxide?
Plasma transports waste Carbon Dioxide produced via aerobic respiration to the lungs for exhalation
2.60: How does plasma transport digested food?
Plasma transports digested food to respiring cells for assimilation in the form of simple sugars (e.g glucose) and Amino acids
2.60: How does plasma transport urea?
Plasma transports waste substances for removal out of the body - Plasma transports Urea from liver to the kidney for excretion
2.60: How does plasma transport hormones?
Plasma transports Hormones produced by Endocrine glands to target organs to stimulate change
2.60: How does plasma transport heat energy?
As Plasma is mainly composed of Water which possesses high specific heat capacity, this allows Plasma to maintain a constant body temperature optimum for enzyme activity for metabolic reactions to occur (optimum body temperature is 37°C)
